Fibre: types, collection and preservation; Identification and comparison of fibres: Microscopic examination, dye composition, chemical composition, significance of match, floatation, solubility and flame test; Analytical techniques in fibre examination

2. Trace evidence ubiquitous type
Higly unique based on utilty
Color is another powerful discriminating characteristic

3. Acetate •Cellulose acetate
Acrylic •85% by weight of acrylonitrile units
Anidex •at least 50% by weight of one or more esters of a monohydric alcohol and acrylic acid
Aramid •synthetic polyamide in with at least 85% of the amide linkages to two aromatic rings
Glass •glass
Lyocell •precipitated cellulose
Metallic •metal, plastic-coated metal, metalcoated plastic, or a core completely covered by metal
Modacrylic •at least 35% by weight of acrylonitrile units
Novoloid •at least 85% of a long-chain polymer of vinylidene dinitrile
Nylon •synthetic polyamide less than 85% of the amide linkages are attached directly to two aromatic rings
Olefin •at least 85% by weight of ethylene,propylene, or other olefin units
Polyester •at least 85% by weight of an ester or a substituted aromatic carboxylic acid
Rayon •regenerated cellulose
Saran •t least 80% by weight of vinylidene chloride units.
Spandex •at least 85% of a segmented polyurethane
Vinal •at least 50% by weight of vinyl alcohol
Vinyon •at least 85% by weight of vinyl chloride units

4. manufactured fiber
is fibers produced
from fiber-forming
substances, which
may be synthesized
polymers, modified
or transformed
natural polymers, or
glass
Natural fiber that
exists as a fiber in
its natural state
Fibers can also be
designated by their
chemical make-up as
either protein,
cellulosic, mineral,
or synthetic
Based on length,
fibers are classified
as either filament
(indefinite length) or
staple fiber ( cut
lengths of filament,
typically being 7/8–8
inch in length.

5. Bast (stem)Fibers :
Flax(linen) (Linum
Usitatissimum)
Jute ( Corchorus Capsularis)
Ramie ( Boehmeria Nivea)
Hemp (Cannabis Sativa)
Leaf fibers:
Sisal ( Agave
Sisilana)
Abaca (Musa textilis)
Seed fibers:
Cotton (Genus
Gossypium)
Kapok ( Ceiba
Pentandra )
Coir (Coco
Nucifera)

7. Yarn is a term for
continuous strands of
textile fibers, filaments, or
material in a form suitable
for weaving, knitting, or
otherwise entangling to
form a textile fabric

8. Guiding rules for fiber recovery include
• follow the GIFT principle, or ‘get it first time’ – this includes scene recovery;
• treat items to be searched gently to minimize loss or disturbance of trace materials;
• if trace materials are visible, remove by hand or using forceps;
• systematically tape lift items using a grid search pattern;
• do not shake or scrape items as these techniques have been shown to be inefficient and will
also destroy location evidence;
• as a final technique, vacuuming may be considered but this is normally only used for large
and difficult-to-access areas

9. Fiber Microscopy
Source: JM Hemmings 2013

10. Color (in
terms of hue,
saturation,
lightness)
Diameter
(natural fiber
has more
variability
along length
than
manufactured
fiber)
Delustrant
(titanium
dioxide added
in manmade
fiber to reduce
luster/ vary
based on
quantity,
shape, size
and
distribution)
Cross
sectional
shape (shape
of transverse
cross section)
Physical features that can be compared at stage of
microscopy:
Source: JM Hemmings 2013

11. Draw
marks
Fine
striations
(Rayon
most
common)
Twist/
convolutions/
Crimp
Voids
(irregular air
spaces)
Internal
channels
(sports
apparel)
Physical features that can be compared at stage of
microscopy:
Source: JM Hemmings 2013

12. Microscopic View – Fibre Identification
MICROSCOPIC VIEW – FIBRE IDENTIFICATION
FLAX:
Longitudinal View : Long, Transparent,
cylindrical and has harrow lumen running through
centre.
Cross sectional view : The cell wall appears thick
and polygonal in shape.
JUTE:
Longitudinal View : Cross wise marks called
nodes or joints.
Cross sectional view : a small central canal.
Several sided or polygonal with rounded edges.
WOOL:
Longitudinal View : Irregular and roughly
cylindrical, prominent scale marking or flattened
plates..
Cross sectional view : Oval to circular with variation
in diameter medulla and variable in size.
FLAX
JUTE
WOOL

13. COTTON:
Longitudinal View : Ribbon like structure flattened with
frequent convolutions.
Cross sectional view : Flat elongated or kidney bean like

14. Microscopic View – Fibre Identification
MICROSCOPIC VIEW – FIBRE IDENTIFICATION
VISCOSE:
Longitudinal View : Uniform diameter with striation
running parallel to the fibre axis.
Cross sectional view : has a irregular cross section.
POLYESTER:
Longitudinal View : Very regular, rod like appearance.
Cross sectional view : Circular in cross section.
NYLON:
Longitudinal View : Very regular, rod like appearance.
Cross sectional view : Circular in cross section.
ACRYLIC :
Longitudinal View : Rod like with smooth surface and
profile.
Cross sectional view : Nearly round or bean shaped.

15.  Behaviour of the fibre when exposed to a
flame depending on the chemical
composition of the fibre.
 In this method a small tuft of fibre is held by
forceps for about 10 s in the flame of a
burner and then removed
 This method is very quick and can be
performed almost anywhere.
 However, the test is subjective and
destructive, consumes a considerable
amount of material and can produce
toxic fumes sometimes.
Behaviour of fiber Cellulosic fibres Wool Silk
Shrinks from
flame
Yes NO NO
Melts near
flame
no yes yes
Smell Burnt paper Burnt hair Burnt hair
Appearance of
ash
Small, light grey Lumpy, blistered,
irregular, black ash,
brittle, breaks easily
Soft, round, black
bead, brittle,
pulverizes easily

16.  The generic fiber types are identified by the
solubility of the fiber in various reagents and
comparing the data (insoluble, soluble and swell) to
the known solubility of several fibers.
 The reactivity of textile fibers to various solvents
such as suphuric acids, sodium hypocrite, sodium
hydroxide, cupprammonium etc., is different
depending upon the chemical composition of the
fibers
 Solubility tests are easy to perform and can be
carried out in test tubes on macroscale or on
the stage of a microscope (ideally used for just
such test)
• Floatation of fibres in different chemicals like
alcohol, Carbon tetrachloride, Chloroform,
methyl salicylate, ortho-dichlor benzene etc. is
observed.
• Degrease a small sample of the fibre with
petroleum ether.
• Place fibre in the test liquid and push below
surface by means of a glass rod. The liquid
should be illuminated transversely and viewed
against a black background to observe whether
the sample floats to the surface or sinks.

17.  The IR spectra of fibres are obtained by a double-beam
spectrophotometer or by a Fourier transform infrared (FTIR)
spectrophotometer.
 The identification of generic fibre types in question is made by
comparing the absorption spectrum of questioned fibres with
reference spectra of known samples .
 When the IR radiation interacts with a fibre, certain frequencies of
energy are absorbed while others are transmitted or reflected
depending on the functional groups (bonds) of the fibre which is
used as a means for identification.
 IR spectrometer is expensive, it offers an unambiguous means of
chemically identifying unknown fibres. Furthermore, when only few
fibres are available, this method is found to be the most valuable
single test.
 The natural fibres exhibit more intrasample variation in the
absorption spectrum compared with synthetic fibres.
 The amount of twist in the fibres should be reduced by teasing
apart and straightening the fibres before FTIR test

18. Source : Nayak 2020

19. Source : Nayak 2020

20. The application of Raman
spectroscopy to forensic
fiber analysis is mainly
focused on
(1) determining the generic
fiber class and
possibly its subclass
(2) comparing the dye
spectrum of fiber traces and
control sample; and
(3) the identification of
dyes.
RAMAN spectra analysis
Source :Dewael 2016

21. Source :Dewael 2016

22.  Microspectrophotometry (MSP) is a combination of
microscopy and spectrometry.
 It enables the measurement of a spectrum of a very
small sample (approximately 100 μm2 ) and
examination of its morphology.
 The MSP technique is fast and non-destructive, which
makes it widely used in different fields.
 Fibers are typically analyzed using the transmission
mode.
 The application of the transmission mode of MSP in fiber
comparison requires special sample preparation, i.e.,
embedding in a mounting medium (such as glycerin)
on glass/quartz microscope slides.
 Although the Vis region (400–760 nm) is most
frequently used, UV–Vis (200–760 nm) and
fluorescence MSP can provide more information and
better discrimination.
 Dyed fibers could be analyzed under glass mount by
UV–VIS microspectrophotometry from 320 nm to 770
nm.
 For fiber types with little or no polymeric UV spectral
interference, additional spectral information could be
obtained from UV–VIS analysis on quartz slides,
measured from 240 nm to 770 nm
Source :HU 2020

23.  TLC is a common tool used for the
comparison of fiber dyes in many
forensic laboratories, but only limited
chemical identification is possible with it.
 TLC can be used with other techniques
such as microscopy and UV–vis
microspectrophotometry in the
comparison of fiber batches.
 TLC can separate more dye classes
than other technique can do.
 TLC requires relatively large quantities
of dye and different solvent systems for
different dye classes.
 High-performance liquid chromatography (HPLC) is
another technique that is more advantageous than TLC
and UV–vis mass spectrophotometry in the analysis of
dyed fibers.
 HPLC gives better resolution and sensitivity.
 Furthermore, it can be used for the quantification of
dye classes.[78]
 Different practical considerations come into play
when an HPLC system is used for fiber dye analysis
eg. organic solvents that have been used for the
extraction of dyed fiber may interfere with the UV–vis
detector.
 Some of the extracted dye classes may degrade, so
low extraction temperatures are required for
extractions.
 Reversed-phase HPLC separation of dyes for the
charged dye classes has been used, and anionic dyes
have been separated more successfully compared with
cationic dyes.
 Even then, however, gradient elution may be required
to separate complex dye mixtures;
 shorter fiber lengths of light dyes upon extraction
may also yield insufficient amounts for analysis.

24.  Capillary electrophoresis (CE) is an
excellent technique for the analysis of dyes,
because many dyes are ionic depending on
pH.
 CE is more advantageous compared with
other techniques in its efficiency, selectivity,
shorter analysis times, ease of handling,
low organic solvent consumption, low
sample requirement (less than 50 nl),
relatively low running cost
 CE cappilaries are reusable, inexpensive,
used at pH higher than that of silica based
HPLC Column.
 Acidic basic and reactive dyes could be
separetd using CE.
 CE/MS provide semi quantitative
estimation
Source :Farah 2015

25.  Ultra-performance liquid
chromatography (UPLC) is another
technique for the sensitive comparison
of fiber dyes.
 This method is often connected with
mass spectrometer in providing
chemical specificity.
 UPLC is advantageous for rapid
analysis by using high-pressure pumps
(capable of moving samples and mobile
phases through columns packed with
smaller-diameter (1.7 μm) stationary
phase particles.
 Therefore, UPLC is able to achieve
very high-resolution separations in
very short analysis time